1. Field of the Invention
This invention relates to an optical scanning technology. In particular, it relates to an optical device capable of providing multiple-resolutions for copiers, facsimiles, and scanners, among others. Upon optical scanning, optimal optical resolution is provided for different sizes of objects to be scanned, thereby enhancing the optical resolution upon processing and further enhancing the image quality.
2. Description of the Related Art
Office products such as copiers, facsimiles, and scanners already play a vital role in this modern hustling and bustling society. Copiers duplicate text pages or image objects and enable knowledge to be rapidly distributed; facsimiles transmit text pages or image objects through telephone lines to a remote location without the lengthy delay of postal delivery; scanners convert text pages or image objects into an electronic file for easy transmission or storage. However, these products all require a pre-scanning of the text or image objects.
The optical path and the focus position of the lens are fixed in the optical processing devices built into currently available copiers, facsimiles, and scanners. Therefore, in optical scanning, the maximal optical resolution is determined and fails to adjust relative to the size of the objects. Software applications use interpolation to increase dots per inch (dpi) for a finer touch of the image. However, such software applications for increasing dpi only improve the image after magnification and do not really enhance optical resolution.
A method of providing variable resolutions for scanners, facsimiles and copiers has been disclosed in the Taiwanese Patent Publication No. 281851. In said method, a variable resolution is provided through a charge-coupled device and a position change of the zoom lens. However, this method provides for any change of resolution; it is not limited to common sizes such as A4, B4 and B5. Such a continuum of possible resolutions is unnecessary, and because it requires two driving motors for respectively driving the charge-coupled device and the zoom lens, the manufacturing cost and thus the retail price for consumers is increased. In addition, the need to simultaneously adjust the charge-coupling device and zoom lens complicates the focusing procedure.
Accordingly, an object of the invention is to provide a multiple-resolution optical device that renders through a movement of lenses the optimal optical resolution for various sizes of objects to be scanned.
Another object of the invention is to provide a multiple-resolution optical device capable of enhancing both the optical resolution during optical processing and the image quality.
The aforementioned objects of this invention can be achieved by providing a multiple-resolution optical device used to scan objects of variable sizes in various resolutions and form corresponding images onto an image sensor. The multiple-resolution optical device according to the present invention comprises a light source, a mirror set, and a lens set. The mirror set reflects the light source projected onto the object and provides a plurality of optical paths. The lens set selects one of the optical paths to provide an object distance and an image distance whereby the corresponding image is clearly formed on the image sensor in response to said size. Hence, an optimal resolution is acquired and the optical resolution for the optical scan processing is substantially enhanced.